Air classifier



Feb. 28, 1928.

A. H. STEBBINS AIR CLASSIF IER 2 sheets sneet 1 Filed Sept. 24, 1926 ATTCkA/Ey Patented Feb. 28, 1928.

UNITED STATES 1,660,683 PATENT OFFICE.

ALBERT H. STEBBINS, 0F LOS ANGELES; CALIFORNIA.

AIR CLASSIFIER.

Application filed September 24, 1926. Serial No. 137,596.

This invention relates to an air classifier and also to a series of air classifiers arranged one above the other in stacked relation to subject the materials to successive treat-- ments.

It is frequently desirable in the treatment of ores and other materials to effect the separation of extremely fine dust-like particles from slightly larger dust-like particles, but such minute particles are extremely difiicult to separate due to their tendency to remain suspended in the air employed in effecting their separation.

When the average particles being treated have the'approximate size of the openings of a 100-mesh screen or larger, they maybe separated fairly satisfactorily by a single air treatment, but when the particles to be treated are extremely small (say of a size l0 pass through a 500-mesh screen, if such fine screens were in use), then an air classification can be effected only by subjecting the particles repeatedly to the gentle separating action of slight air currents.

The present invention therefore contemplates a multiple treatment classifier that conssts 'of a number of similar classifying receptacles that are connected in series so that the heavier particles pass from one re: ceptacle to another and are subjected in each receptacle to gentle air currents that serve to carry off some of the finer particles. i

One-important feature of the present invention resides in the arrangement of the classifying receptacles one above the other in stacked relation so that the heavier parti-, cles flow by gravity from one receptacle to another.

Another feature of the invention resides in the simple construction whereby air under pressure is supplied to each receptacle from a single blast fan or other source of air supply, and also inthe construction whereby a single suction conduit serves to remove the air and particles suspended therein from each receptacle. I

Another feature of the invention resides in the construction of the individual classifying receptacles whereby the heavier particles are subjected to the lifting action of jets of a r as they approach the discharge opening at the lower end of each receptacle. These jets of air serve to disengage from the larger particles and to carry upwardly the fine par-j ticles which tend to cling to such largerparticles.

Still another feature of the invention resides in the construction whereby the air rising in each classifying receptacle is given a whirling movement that serves to throw the heavier particles outwardly against the Walls of the receptacle.

Other features of the invention and novel combination of parts, in addition to the above, will be hereinafter described in connection with the accompanying drawings which illustrate good practical forms of the invention.

In the drawings- Fig. 1' is a side elevation of a multiple treatment classifier constructed in accordance with the present invention;

Fig. 2 on an enlarged scale is a vertical sectional view through the upper portion of the multiple classifier of Fig. 1;

Fig. 3 on a still larger scale is a sectional view taken on the line 3 3 of Fig. 2;

Fig. 4 is-a sectional view taken on the line 1- 1 of Fig. 2;

Fig. 5 is a side elevation of a slightly different multiple treatment classifier from that of Fig. 1; and

Fig. 6 on an "enlarged scale is'a vertical sectional view through a modified construction for supplying air to the lower portion of a classi er.

The mu tiple treatment classifier of Fig. 1v is formed of a number of separate .classifiers 1Q which are arranged one above the other in stacked relation? Each of the classifiers 10, in the construction shown, is formed of a closed receptacle which preferably has the configuration best shown in Fig. 2, whereinit will be seen that the upper portion of each receptacle 10 has a relatively large annular portion, as indicated by 11, while the lower portion of each receptacle is conical in shape and has the inclined walls 12 which converge towards their lower end and serve to direct the heavier particles into the discharge opening 13 at the lower end of a receptacle. The upper end of each receptacle is closed by a cover 14.

The construction of the receptacles 10 is such that the heavier materials that settle in one receptacle will slide down the inclined walls 12 through the discharge opening 13 into the next receptacle, so that the heaviest materials pass successively through any desired number of receptacles 12, and in each of these receptacles they are subjected to the action of rising currents of air which serve to gradually remove from the heavier particles the lighter particlesthat tend to cling to the heavier particles.

As above indicated an important feature of the present invention resides in the construction whereby the heavier particles that settle in a classifier 10 must travel across a number of air jets near the lower end of the receptacle before they can escape through the discharge opening 13. In the construction shown in Figs. 1, 2 and 3, these air jets are produced by giving the lower portion of each receptacle 10 the stepped construction best shown in Fig. 2 wherein it will be seen that such stepped portion consists of the annular upright portions 15 that are connected by the inclined portions 16. Each annular portion 15 has a number of slots or apertures 17 formed through its wall and these slots are provided with the inwardly extending lips 18, the arrangement being such that the air passing inwardly through the slots 17 is given a rotative movement as it moves upwardly within the receptacle. The upper ring portions 15 are larger in diameter than the lower ring portions and the upper ring portions'are therefore provided withm'ore apertures 17 than the lower or small rings 15.

In order to force air inwardly through the apertures .17, a casing 19 is provided about the stepped portion of each receptacle 10, and air under pressure is supplied to each casing 19 by atangentially disposed pipe 20 that leads from a conduit 21 disposed alongside the stack of receptacles.

The conduit 21 preferably decreases in diameter in an upward direction to accommodate the volume of air passing through different portions of the conduit and air under pressure may be supplied to this conduit by a blast fan 22 that is connected by a pipe 23 to the conduit.

Since the receptacles 10 increase in size in an upward direction, the air rising in the receptacles is permitted to expand and spread out laterally as itrises, with the result that its lifting effect upon the particles suspended in the air decreases as'the air approaches the upper part of a receptacle. This gives the heavier particles an opportunity to settle upon the inclined walls 12, and the slope of these walls is suiiiciently steep to cause the materials to slide down the walls into the vicinity of the apertures 17 for further treatment. In this manner the particles may be treated a number of times in any one of the receptacles before they tfinally escape through the opening 13 past the air jets, or are carried upwardly out of the receptacle through the air discharge outlet 24.' i

The whirling movement imparted to the airwithin the receptacles by the construction of the apertures 17 described serves to spread the air out in the receptacles and also to throw the particles outwardly by centrifugal force against the walls 12 to slide down these inclined walls.

Each of the receptacles 10 is preferably connected to an air exhaust conduit 25 disposed alongside the stack of receptacles and this conduit preferably increases in diameter in an upward direction to accommodate the increased volume of air drawn into the same, and the upper end of this conduit may be connected to a suction dust extractor 26. The heavier particles that may be carried by the air into the conduit 25 are subjected to a settling or retreatinent action therein, and the retreatment of the particles in this conduit is promoted by giving a retative movement to the air therein which helps to work the heavier particles outward- 1y against the walls of the conduit. The desired rotative'movement is imparted to the air within the conduit 25 by constructing the connecting pipes 27 as best shown in Fig. 4 wherein it will be seen that each pipe 27 direct-s its air more or less tangentially into the suction conduit. Theparticles that settle in the conduit 25 pass through a small pipe 28 into a closed receptacle 29.

The materials to be treated may be delivered to the uppermost receptacle 10 from a feed hopper 30, and in order to secure a uniform flow of materials from the hopper, a rotating feed disk 31 may be provided which may be rotated by a belt engaging the pulley 32. In order to spread the materails out in the uppermost receptacle they may be delivered upon the cone deflector 33 and around which is placed the annular wall 34 arranged to prevent the rising air within the receptacle from reaching the feed pipe 35.

lVhen the materials being treated contain exceptionally fine particles, these fine particles may tend to pack or cling to the side walls of the classifiers. It may therefore be desirable to make the walls 36 of the receptacles near the upper end of the multiple classifier steeper than the walls of the lower receptacles, as shown in the modified construction of Fig. 5. As soon as the exa large number of apertures 38 are formed in the'inclined walls 39.

Asa result of the multiple classifier construction described, any desired number of individual classifiers may be arranged in stacked relation one above the other, and since the individual classifiers may be rela-. tively small, a large number of these classifiers (say fifty or more) may be assembled one above the other in stacked relation Without producing an excessively tall tower.

This large number of classifiers may be operated from one air blast pipe and from one air exhaust ipe, and may be operated from a single feed hopper. The volume of air required to operate a large number of the classifiers will be relatively small because of the necessity of employing gentle air currents in separating fine dust-like particles. The heavier materials as they pass downwardly through the difierent classifiers are subjected time and time again to the action of rising currents of air that gently carry ofi the lighter particles. The lowermost receptacle 10 may be discharged into the closed bin 40.

What is'claimed is 1. An air classifier comprising in combination, a closed receptacle having an air discharge opening near its upper end and side walls that converge downwardly to.- wards a central opening at its lower end through which the heavier materials are discharged, means for introducing air under pressur'einto the lower portion of the receptacle ata multiplicity of points around the material discharge opening and including an aperturcd surface having inclined apertures formed to impart a-rotating spiral movement to the air rising in the receptacle, and means for delivering the materialsto be treated into the upper art of the receptacle so that the heavier particles are carried out. wardly by the rotating air to slide down the side walls of the receptacle across the air inlet openings into the material discharge opening While the light particles are carried by the air upwardly through the air disc a rge opening. 2. An air classifier, comprising in combinatlon, a closed receptacle having a central opening at its lower end and tapered down-' wardly converging walls that direct materials into said opening and also having an air discharge opening near its upper end, the lower end ofthe receptacle being provided with a multiplicity of air inlet aper tures disposed to deliver currents of air through the particles that slide down the walls of the receptacle toward the material discharge opening, said apertures being constructed to impart a spiral movement to the air passing through them to throw the heavier particles outwardly by centrifugal force, a closed casing surrounding the apertured portion of the receptacle, and disposed out of the path of the falling materials, means for forcing air into said casing to deliver.

air under pressure to said apertures, and means for delivering the materials to be treated into the upper part of the receptacle so that the heavier particles settle withinthe receptacle in opposition to the rising air currents while the lighter particles are carried by the air through the air discharge opening.

, 3.An air classifier, comprising in combination, a conical shaped receptac e having a material discharge opening at its lower end and an air discharge opening near its upper end, said receptacle having downwardly converging side walls and a stepped annular portion near its lower end that surrounds the material discharge opening and. the stepped portion being. providedwith apertured areas separated by unapertured areas, a closure for the upper end of the receptacle, means for delivering the materials to be treated into the upper ortion of, the receptacle, andlmeans for directing air through said apertures to produce rising .air currents in the receptacle to carry the lighter particles out through saidair discharge carry the lighter particles upwardly toward 'the upper end of each receptacle, and means;

for removing the air and lighter particles, fromeach receptacle so that the; separating air does not pass from one receptacle to the next. .7 I a ,5

5 A multiple treatment classifier, come prising in combination, ,a series of closed classifying receptacles disposed onesabjove the other in stacked relation and constructed 1 l and arranged so that the materials that/settle in one receptacle flow by gravity into the next lower receptacle for further treatment, means for introducin air into the lower or; tion of each receptac e to produce rising air currents that carry the lighter particles/being treated! toward the upper end of thesreceptacle, and means for removing the air and lighter particles from each receptacle so that the separating .air does not passfrom one receptacle tothe other. 1

v6.,A multiple treatment classifier, comprising incombination. a series of similar classifying'receptacles disposed one above the other in stacked relation and constructed and arranged. so that the materials that settle in one receptacle flow by gravity into the next' receptacle for .further treatment, a'suctionthe air and the lighter particles suspended in the air, a connection between each receptacle and said suction conduit for removing the air without causing it to pass from one 5' receptacle to the next, and a blast pipe having connections for delivering air under pressure into the lower portion of each receptacle to produce rising air currents wlthin the receptacles.

7. A multiple treatment classifier, comrising in combination, a series of classifymg receptacles disposed one above the other in stacked relation and each having downwardly converging side walls adapted to direct the materials that'settle in one receptacle into the upper portion of the next lower receptacle for further treatment, means for introducingjets of air through the converging walls of each receptacle so that the particles sliding down the side walls are directed across the air jets, and means for removing from the upper part of each receptacle the air and lightmaterials suspended there in so that the separating air does not pass from one receptacle to the next.

8.- A multiple treatment classifier, comprising in combination, a series of classifying receptacles disposed one above theother and constructed and arranged so that the larger particles that settle in one receptacle flow by gravity into the next receptacle for further treatment, means for delivering clean air under pressure into the lower portion of each receptacle to produce rising air currents that pick up the lighter particles, and means for removing from each receptacle the air and the lighter particles carried by the'air so that the separating air does not pass from one receptacle to another.

9. A multiple treatment classifier, comprisingin combination, a series of classifying receptacle disposed one above the other in stacked relation and arranged so that the heavier particles that settle in one recep- 5 tacle are directed into ceptacle for further treatment, each receptacle being provided with a converging lower end having a central opening through which the heavier particles pass into the next re- 5 ceptacle, means for introducing rising currents of air into the receptacle around said discharge opening to remove the lighter particles from the heavier particles, and means for removing from the upper portion of each receptacle the air and lighter particles suspended in the air so that the air is supplied to and exhausted from each receptacle independently of the other receptacles.

10. A multiple treatment classifier, comprising in combination, a series of classifying receptacles disposed one above the other and arranged so that the heavier particles that settle in one receptacle flow by gravity into the next receptacle for further treatment,

55 each receptacle being provided with a. conthe next lower re-- verging lower'end having a central opening through which the heavier particles pass into the next receptacle and having a series of air apertures formed in the receptacle about said opening, a casing surrounding the apertured portion of each receptacle, means for forcing air into each casing to form jets of air entering the receptacles through said apertures, and means for removing from the upper part of each receptacle independently of the other receptacles the air and the lighter particles sus ended in the air.

11. A mu tiple treatment classifier, com prising in combination, a. series of classify-, ing receptacles disposed one above the other and arranged so that the heavier particles that settle in one receptacle flow by gravity into the next receptacle for further treatment, means for introducing air into the lower portion of each receptacle with an upward spiral movement that causes it to spread out and throw the heavier particles against the walls of the receptacle, and means for removing from the upper part of each receptacle independently of the other receptacles the air and the lighter particles suspended in the air.

12. A multiple treatment classifier, comprising in combination, a series of classifying receptacles disposed one above the other in stacked relation and arranged so that the heavier particlesthat settle in one receptacle flow by gravity into the next lower receptacle, means for introducing air into the lower portion of each receptacle to rise therein so that the materials within each receptacle are subjected to the separating action of rising air currents, a vertical'conduit disposed adjacent the stack of receptacles and in which the finer materials that pass from the receptacles into the stack are subjected to a reclassifying action, means for exhausting air from the upper end of the conduit, and a pipe between each receptacle and said conduit and arranged to deliver the air passing through the pipe approximately tangentially into the conduit to impart a rotating movement air in the conduit. 1

13. A multiple treatment classifier, comprisin in combination, a series of closed classi ying receptacles disposed one above the other in stacked relation and arranged so that the heavier particles that settle in one receptacle will flow by gravity into the next lower receptacle, means forsupplying air under pressure to each receptacle, comprising a conduit extending lengthwise of the stack and provided with branch pipes for delivering air into the lower portion of each receptacle to rise therein so that the materials within each receptacle are subjected to the separating action of rising air currents, and means for removing air from each receptacle without causing the air to pass from to the volume of I,

one receptacle to the nextond conduit extending iengthwise of the stack and provided with branch pipes leadingfrom the upper portion of each recep- 5 tacle to the conduit.

14. A multi le treatment classifier, comprising in com ination, a stack formed of a large number of small classifying receptacles disposed one above the other and ar- 10 ranged so that the heavier particles will'fiow by gravity from one receptacle to the next,

comprising a see an air supply conduit extending lengthwise of said stack and provided with branch pipes leading into. the lower end of each receptacle, an air exhaust pipe extending length In testimony whereof, I have signed my 2 name to this specification. v

' ALBERT H.-STEBBINS; 

